1. Field of the Invention
The present invention relates to positioning devices, more particularly, to single-axis drive systems for precision positioning of machine stock for cutting or the like.
2. Description of the Related Art
Single-axis programmable positioning devices for precision positioning of work pieces in cutting machines, also know as linear gauges and adjustable stops, are known. The positioning basic device has a linear rail on which rides a trolley. The trolley travels back and forth on the rail by means of a drive mechanism that is controllable either manually, under computer control, or a combination of the two. The trolley includes a stop, which contacts the work piece. As the trolley moves, the stop pushes the work piece linearly through a work area. The work area may be, for example, under a saw or a drill press.
Typically, the positioning device can be programmed with a sequence of positions to which the trolley will move. In some scenarios, the trolley is moved to the next position by an operator touching a button. In other scenarios, the trolley moves to the next position on completion of an action. For example, when used with a drill press, the act of raising the drill press causes the trolley to move to the next position.
In some configurations, the positioning device mounts along side a roller table on which the work piece moves as it is being pushed by the positioning device.
In the current art, three types of drive systems are used, screw drives, rack and pinion drives, and belt drives. In a screw drive, a motor spins a threaded rod that extends through a threaded aperture on the trolley. As the motor rotates, the trolley moves along the rail. Screw drives are the most accurate. They are found only in high-end (expensive) systems because the very long, machined screw is a costly component.
In a rack and pinion drive, a motor spins a pinion that is meshed with a rack, to which the trolley is mounted. As the pinion turns, the rack and trolley move linearly. Rack and pinion drives are accurate. Like screw drives, they are found only in high-end systems because the very long, machined rack is a costly component.
In a belt drive, a motor drives a belt that extends between a sprockets or pulleys at each end of the rail. The trolley is attached to one location on the belt. As the motor rotates, the trolley moves along the rail. Belt drives are the least accurate because the belt has a tendency to stretch. Because of the lack of accuracy and the low cost of the belt, belt drives are used in low-end systems.
There exist a need for a single-axis programmable positioning device that approaches the accuracy of the screw or rack and pinion drive at the cost of a belt drive.